Mass produced clock operated thermostats are normally installed in a variety of different types of heating and cooling applications. The same basic thermostat may be used for control of a forced air heating and cooling system, all electric systems, normal hydronic systems, and oversized hydronic systems. Also, utilized in this area are multistaged heat pump devices that utilize the multiple stages for heating and cooling, sometimes combined with auxiliary heat. Each of these types of installations have entirely different characteristics in response to a normal setup, or setback, that is accomplished for energy savings by a clock thermostat.
While attempts have been made to provide adjustments in the cycling rate of a thermostat for a particular type of heating plant, this type of accommodation normally will not provide good comfort control when the thermostat calls for sudden setup or setback temperature that has been programmed into the thermostat. These major changes in the setpoint of the thermostat can cause significant overshoot problems in both single stage and multistage type environments. The patent application referred to in the above cross-reference is particularly adapted for solution of this problem in single stage type installations.
Typically, a substantial morning pickup is provided by clock operated thermostats. The space temperature is normally controlled at a relatively low temperature during the night to save energy. In the morning, a setup occurs in order to move the space temperature from the lower energy saving level to a desired higher comfort level. This typically locks the heating plant into a full "on" state and the space temperature rises at a rate that is a function of the particular parameters of the heating plant and the environment in which it is used. This arrangement causes a substantial overshoot of the space temperature compared to the setpont temperature that is being called for by the clock thermostat. Ordinarily, in a hour or two. this overshoot corrects itself, but this is an undesirable result of the sudden setpoint change that occurs when pickup is programmed into this type of a thermostat.